The present invention relates to an enciphering method, deciphering method, recording and reproducing device, deciphering device, deciphering unit device, recording medium, recording-medium manufacturing method, and key control method which are for preventing the digitally recorded data from being copied from a recording medium.
Compact disks and laser disks have been available as recording mediums that record digitized data (e.g., documents, sound, images, or programs). Floppy disks and hard disks have been used as recording mediums for computer programs and data. In addition to those recording mediums, a DVD (digital video disk), which is a large-capacity recording medium, has been developed.
Since the aforementioned various digital recording mediums record the digital data (including the compressed or encoded data, which can be decoded later) as it is, the recorded data can be copied easily to another recording medium without impairing the quality of sound or the quality of image, which enables a large number of reproductions to be made, contributing to literary piracy.
In summary, when the data is copied from a digital recording medium, the data can be copied with the sound quality and picture quality of the master remaining unchanged, or without the deterioration of sound quality or picture quality. This has caused the problem of permitting the wrongful conduct of making unauthorized copies of the original and selling them without paying a royalty.
Accordingly, it is an object of the present invention to provide an enciphering method, deciphering method, recording and reproducing device, deciphering device, deciphering unit device, recording medium, recording-medium manufacturing method, and key control method which are for preventing an unauthorized copy of digital recording mediums.
According to one aspect of the present invention, there is provided an enciphering method comprising the steps of: enciphering data with a first key; and enciphering the first key with each of a plurality of predetermined second keys.
According to another aspect of the present invention, there is provided a recording medium having information items recorded thereon, the information items comprising: first information obtained by enciphering data with a first key; and second information obtained by enciphering the first key with each of a plurality of predetermined second keys.
According to another aspect of the present invention, there is provided a recording medium manufacturing method comprising the steps of: obtaining first information by enciphering data with a first key; obtaining second information obtained by enciphering the first key with each of a plurality of predetermined second keys; and recording the first and second information on the same recording medium.
According to another aspect of the present invention, there is provided a deciphering method comprising the steps of: inputting first information obtained by enciphering data with a first key and second information obtained by enciphering the first key with each of a plurality of predetermined second keys; deciphering the first key using at least one of the second keys to obtain the first key; determining by a specific method whether or not the obtained first key is correct; and deciphering the data using the first key after the determination to obtain the data.
According to another aspect of the present invention, there is provided a deciphering device comprising: input means for inputting first information obtained by enciphering data with a first key and second information obtained by enciphering the first key with each of a plurality of predetermined second keys; storage means for storing at least one of the second keys; and deciphering means for deciphering the first key from the second information inputted from the input means using at least one of the second keys in the storage means, determining by a specific method whether or not the obtained first key is correct, and deciphering the data from the first information using the first key after the determination to obtain the data.
According to another aspect of the present invention, there is provided a recording and reproducing device comprising: reading means for reading first information and second information from a recording medium on which the first information obtained by enciphering data with a first key and the second information obtained by enciphering the first key with each of a plurality of predetermined second keys have been stored; storage means for storing at least one of the second keys; and deciphering means for deciphering the first key from the second information read by the reading means using at least one of the second keys in the storage means, determining by a specific method whether or not the obtained first key is correct, and deciphering the data from the first information using the first key after the determination to obtain the data.
According to another aspect of the present invention, there is provided a key control method comprising the steps of: causing a first caretaker to take custody of a plurality of predetermined second keys; causing a second caretaker to take custody of first information obtained by enciphering data with a first key and second information obtained by enciphering the first key with each of the predetermined second keys; and causing a third caretaker to take custody of at least one of the second keys.
According to another aspect of the present invention, there is provided a deciphering device comprising: reading means for reading first information, second information, and third information from a recording medium on which the first information obtained by enciphering data with a first key, the second information obtained by enciphering the first key with each of a plurality of predetermined second keys, and the third information used for key determination have been stored; storage means for storing at least one of the second keys; first deciphering means for deciphering one of the enciphered first keys selected in the order determined from the second information using one second key selected in the order determined from the second keys stored in the storage means, determining on the basis of the deciphering result and the third information whether or not the first key obtained by the deciphering is correct, and repeating the selection and the determination until the first key determined to be correct has been obtained; and second deciphering means for deciphering the data from the first information using the first key the first deciphering means has determined to be correct.
According to another aspect of the present invention, there is provided a deciphering device comprising: a first unit built in a driving unit of a recording medium or connected to the driving unit of the recording medium without the CPU bus of a computer, including: means for transferring first information obtained by enciphering the data read from the recording medium with a first key, second information obtained by enciphering the first key with each of a plurality of predetermined second keys, and third information used for key determination in such a manner that at least the second information and third information are transferred safely without being externally acquired; and a second unit connected to the first unit via the CPU bus of the computer including: means for receiving the first information, second information, and third information from the first unit via the CPU bus of the computer in such a manner that at least the second information and third information are received safely without being externally acquired; storage means for storing at least one of the second keys; first deciphering means for deciphering one of the enciphered first keys selected in the order determined from the second information using one second key selected in the order determined from the second keys stored in the storage means, determining on the basis of the deciphering result and the third information whether or not the first key obtained by the deciphering is correct, and repeating the selection and the determination until the first key determined to be correct has been obtained; and second deciphering means for deciphering the data from the first information using the first key the first deciphering means has determined to be correct.
According to another aspect of the present invention, there is provided a deciphering device comprising: reading means for reading first information, second information, third information, and fourth information from a recording medium on which the first information obtained by enciphering a third key with a first key, the second information obtained by enciphering the first key with each of a plurality of predetermined second keys, the third information used for key determination, and the fourth information obtained by enciphering data with the third key have been stored; storage means for storing at least one of the second keys; first deciphering means for deciphering one of the enciphered first keys selected in the order determined from the second information using one second key selected in the order determined from the second keys stored in the storage means, determining on the basis of the deciphering result and the third information whether or not the first key obtained by the deciphering is correct, and repeating the selection and the determination until the first key determined to be correct has been obtained; second deciphering means for deciphering the third key from the first information using the first key the first deciphering means has determined to be correct; and third deciphering means for deciphering the data from the fourth information using the third key obtained by the second deciphering means.
According to another aspect of the present invention, there is provided a deciphering method comprising the steps of: reading first information, second information, and third information from a recording medium on which the first information obtained by enciphering data with a first key, the second information obtained by enciphering the first key with each of a plurality of predetermined second keys, and the third information used for key determination have been stored; deciphering one of the enciphered first keys selected in the order determined from the second information using one second key selected in the order determined from the second keys, determining on the basis of the deciphering result and the third information whether or not the first key obtained by the deciphering is correct, and repeating the selection and the determination until the first key determined to be correct has been obtained; and deciphering the data from the first information using the first key determined to be correct.
According to another aspect of the present invention, there is provided a deciphering method comprising the steps of: transferring first information obtained by enciphering the data read from a recording medium with a first key, second information obtained by enciphering the first key with each of a plurality of predetermined second keys, and third information used for key determination from a first unit built in a driving unit of the recording medium or connected to the driving unit of the recording medium without the CPU bus of a computer to a second unit via the CPU bus of the computer in such a manner that at least the second information and third information are transferred safely without being externally acquired; and in the second unit, deciphering one of the enciphered first keys selected in the order determined from the second information using one second key selected in the order determined from the second keys stored in the storage means, determining on the basis of the deciphering result and the third information whether or not the first key obtained by the deciphering is correct, repeating the selection and the determination until the first key determined to be correct has been obtained, and deciphering the data using the first key determined to be correct.
According to another aspect of the present invention, there is provided a deciphering method comprising the steps of: reading first information, second information, third information, and fourth information from a recording medium on which the first information obtained by enciphering at least a third key with a first key, the second information obtained by enciphering the first key with each of a plurality of predetermined second keys, the third information used for key determination, and the fourth information obtained by enciphering data with the third key have been stored; deciphering one of the enciphered first keys selected in the order determined from the second information using one second key selected in the order determined from the second keys, determining on the basis of the deciphering result and the third information whether or not the first key obtained by the deciphering is correct, and repeating the selection and the determination until the first key determined to be correct has been obtained; deciphering the third key from the first information using the first key determined to be correct; and deciphering the data from the fourth information using the third key obtained.
According to another aspect of the present invention, there is provided a deciphering unit device that receives information via the CPU bus of a computer from a bus transfer unit built in a driving unit of a recording medium or connected to the driving unit of the recording medium without the CPU bus of the computer and deciphers data on the basis of the information, the deciphering unit device comprising: means for receiving first information obtained by enciphering the data read from the recording medium with a first key, second information obtained by enciphering the first key with each of a plurality of predetermined second keys, and third information used for key determination from the bus transfer unit via the CPU bus of the computer in such a manner that at least the second information and third information are received safely without being externally acquired; storage means for storing at least one of the second keys; first deciphering means for deciphering one of the enciphered first keys selected in the order determined from the second information using one second key selected in the order determined from the second keys stored in the storage means, determining on the basis of the deciphering result and the third information whether or not the first key obtained by the deciphering is correct, and repeating the selection and the determination until the first key determined to be correct has been obtained; and second deciphering means for deciphering the data from the first information using the first key the first deciphering means has determined to be correct.
In each of the above categories, the data may include at least one of key information, documents, sound, images, and programs.
With the present invention, only the correct party having at least one of the second keys can get the first key and therefore can get the plain data of the data enciphered using the first key. As a result, the wrongful conduct of making unauthorized copies and selling the thus copied mediums can be prevented, thereby protecting copyrights.
Moreover, with the present invention, even if the data flowing over the signal line connecting the enciphering unit to the deciphering unit is stored, the stored data cannot be reproduced or used, because the data is the enciphered data. In addition, because the information necessary for enciphering the data is created on the basis of, for example, random numbers, and cannot be reproduced later, the stored data cannot be reproduced or used, even if the second key (master key) in the deciphering unit has been broken. As a result, the wrongful conduct of making unauthorized copies and selling the thus copied mediums can be prevented, thereby protecting copyrights.
Still furthermore, with the present invention, because the enciphering unit and deciphering unit can be designed separately from the essential portion of the reproducing section of the digital recording and reproducing apparatus, even if the cipher is broken, the enciphering unit and deciphering unit have only to be replaced to overcome this problem.
Additional objects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.